ARRANGEMENT RELATING POWER BACKUP AND METHOD FOR POWER BACKUP

TECHNICAL FIELD

The present invention relates to a method and arrangement in a device comprising a 5 charging capacitor and using the charging capacitor as a power backup.

BACKGROUND OF THE INVENTION

Communication devices, such as cellular telephones, have become increasingly versatile. For example, cellular telephones today often include applications that allow users to do more than just make and receive telephone calls, such as send/receive text messages, o play music, play video games, take pictures, etc. As a result, cellular telephones have become an increasingly common part of every day life for a large number of users.

The functionality of taking pictures and costumers demands imply that more sufficient camera units are incorporated in the mobile phone. It is not unusual that cameras are of high quality with very good resolution also allowing simple or high quality flash function 5 using an intensive light emitting portion. The flash is usually an ordinary or modified camera flash using a flash capacitor.

Of course, in all electrical devices power supply to the electrical parts is a crucial function. In mobile devices, especially, the device is exposed to motion and shakes which may effect some parts of the device. Usually the battery is connected to the electronics by0 means of resilient connectors, which may glitch resulting in malfunction of the device.

It is believed that on/off problems, especially du to glitches, are one of the major sources of irritation for the users, which results in high return rate.

Fig. 1 illustrates a device 100, such as a mobile phone, comprising a housing 101 , a power source such as a battery 1 10, a camera portion 120, controlling electronics 130,5 voltage transforming circuit 140, a flash 150 and flash capacitor 160.

Of course the device comprises other electrical circuits, e.g. transceiver and interface circuits in case of a mobile phone, well known to a skilled person, which are not described herein.

In accordance with prior art, a capacitor charging device for a flash for example disposed in a digital camera is used to charge the flash capacitor of the digital camera so as to provide electricity to the flash. As shown in the example of Fig. 2, the charging device 5 includes a flash capacitor 260, voltage transforming circuit 240, current mode pulse width modulation (PWM) control circuit 231 and charging control circuit 232. The voltage transforming circuit 240 may further include a transformer 241 , diode D1 , resistor R1 and a transistor (MOSFET) Q1 .

When the charging device functions initially, the current mode PWM control circuit 231 o outputs a pulse current I to control the gate-to-source voltage VGS. The charging control circuit 232 controls the pulse width of the current I with a time control capacitor (not shown). Since the capacitance of the time control capacitor is small, the soft start period (i.e. the period for reaching the maximum pulse width of the current I) of the current mode PWM control circuit 231 is very short. Hence, the current mode PWM control circuit 231 5 can output a pulse current I with maximum pulse width in a very short time.

When the pulse current I is "on" (i.e. a state with an output current), the gate-to-source voltage VGS of the MOSFET Q10 is positive and results in an increase of the current ID passing through the MOSFET Q10. While the current ID increases, the transformer 231 generates an induced current IO to charge the flash capacitor 260. When the pulse current0 I is "off" (i.e. a state with no output current), the gate-to-source voltage VGS of the MOSFET Q1 is zero and results in the decrease of the current I ₀ . While the current I ₀ decreases, due to the tremendous reverse resistance of the diode D10, the induced current I ₀ also reduces to zero. Thereby, the flash capacitor 260 can be charged by the induced current I ₀ in the on-off circle of the pulse current I. 5 SUMMARY OF THE INVENTION

The present invention introduces a novel solution for power backup, which eliminates the problems with on/off due to power failure, e.g. because of power source connection glitches. 0 Thus, the present invention according to a first aspect of the invention relates to a method in a device comprising electrical components configured to be supplied with power from a

power source, the device comprising a capacitive element configured to provide a flash with operational power, the method comprising the steps of: sensing power from the power source, redirecting power from the capacitive element to the electrical components if a power supply failure is detected, and adjusting power level from the capacitive 5 element to a level consumable by the electrical components. Most preferably, the capacitive element is a flash capacitor.

The invention also relates to an arrangement in a device comprising: electrical components configured to be supplied with power, a power source for supplying the o components, a capacitive element configured to provide a flash element with operational power. The arrangement comprises: a device for sensing power supplied from the power source, and means for redirecting power from the capacitive element to the electrical components when power from the power source reduces to a predetermined level. Preferably the arrangement may further comprise a power transformer for adjusting power 5 level from the capacitive element to a level consumable by the electrical components. The power supply may be a battery. The capacitive element may be a flash capacitor. The arrangement may further comprise a controller circuit and a switching arrangement. Preferably, the controller circuit receives information about the power supply of the power source to the electrical components. The switching arrangement may be configured to0 supply power from the power source to parts which need electricity. A power backup controller arrangement may be configured to control a power transforming circuit so that power stored in the capacitive element is transformed down to a level usable by the electrical circuits. 5 According to another aspect of the invention a device comprising an image recording arrangement and a flash light, a capacitor for powering the flash light and a power source is provided. The device further comprises an arrangement comprising: a device for sensing power supplied from the power source, and means for redirecting power from the capacitive element to the electrical components when a power from the power source0 reduces to a predetermined level. Most preferably, the device further comprises a communication portion for communication with a communication network. The device may further comprise a housing, a display, control buttons and a keypad. The device may further comprise charging control circuit, a voltage mode circuit, a voltage transforming circuit, a power direction control arrangement and a power directing switch arrangement.5 In an advantages embodiment for charging the capacitor, when the voltage across the

flash capacitor is low, the charging control circuit is arranged to provide a low voltage to activate the voltage mode control circuit, which is arranged to output a voltage, the voltage mode control circuit is arranged to provide a constant current to charge a capacitor of the charging control circuit, whereby the voltage mode control circuit is 5 arranged to increase a pulse width of the pulse voltage according to a voltage across the capacitor, the pulse voltage drives the voltage transforming circuit to provide an induced current to charge the flash capacitor. The power backup controlling arrangement redirects the function of the power transforming circuit so that the power stored in the flash capacitor is transformed down to a suitable level for other electrical circuits in the device. O BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, explain the invention. In the drawings:

Fig. 1 illustrates schematically a state of the art solution,

5 Fig. 2 illustrates schematically an embodiment according to the present invention,

Fig. 3 illustrates a device incorporating an arrangement according to the present invention, and

Fig. 4 illustrates a device incorporating an arrangement according to the present invention in more detail. 0 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A "device," as the term is used herein, is to be broadly interpreted to include a radiotelephone; a personal communications system (PCS) terminal that may combine a cellular radiotelephone with data processing, a facsimile, and data communications capabilities; a personal digital assistant (PDA) that can include a radiotelephone, pager,5 Internet/intranet access, web browser, organizer, calendar, a camera (e.g., video and/or still image camera), a sound recorder (e.g., a microphone), a Doppler receiver, and/or global positioning system (GPS) receiver; a laptop; a GPS device; a camera (e.g., video and/or still image camera); a sound recorder (e.g., a microphone); and any other computation or communication device capable of displaying media, such as a personal0 computer, a home entertainment system, a television, etc.

A "glitch," as the term is used herein, is to be broadly interpreted to include power supply failure or reduction.

As shown in Fig. 3, an exemplary device 300 may include a housing 310, a display 31 1 , control buttons 312, a keypad 313, communication portion 314, a battery 315 and a 5 camera 320. Housing 310 may protect the components of device 300 from outside elements. Display 31 1 may provide visual information to the user. For example, display 31 1 may provide information regarding incoming or outgoing calls, media, games, phone books, the current time, etc. Control buttons 312 may permit the user to interact with device to cause device to perform one or more operations. Keypad 313 may include a

1 o standard telephone keypad. Camera 320 may enable a user to capture and store video and/or images (e.g., pictures). The function of the camera portion together with the power backup portion according the present invention will be described in more detail below. The communication portion comprises parts (not shown) such as receiver, transmitter, antenna etc., for establishing and performing communication with one or several

1 5 communication networks.

The camera portion 320 in conjunction with the power backup portion according to the present invention, as illustrated in Fig. 4, comprises image capturing electronics 321 , camera lens 322, the flash 450, flash capacitor 460, charging control circuit 470, voltage mode circuit 480, voltage transforming circuit 490, power direction control arrangement 20 444 and power directing switch arrangement 445. It should be noted that Voltage mode circuit is optional according to this example and may be left out or substituted with other voltage controlling arrangement.

The operation of the camera per se is assumed to be well known by a skilled person and not described herein in detail.

25 Fore charging the capacitor, when the voltage across the flash capacitor 460 is low, the charging control circuit 470 provides a low voltage to activate the voltage mode control circuit 480 and make it output a (pulse) voltage V1. Then, the voltage mode control circuit 480 provides a constant current to charge a capacitor (not shown) of the charging control circuit 470. At the same time, the voltage mode control circuit 480 increases a pulse width

30 of the pulse voltage V1 according to the voltage across the capacitor. The pulse voltage V1 drives the voltage transforming circuit 490 to provide an induced current 11 to charge the flash capacitor 460. When the flash capacitor 460 is charged completely, the voltage

transforming circuit 490 provides a high voltage V2 to stop the voltage mode PWM control circuit 480 outputting the pulse voltage V1 .

The arrangement of the invention according to this embodiment further comprises a controlling circuit 444 and a switching arrangement 445. The controlling circuit 444 5 receives information about the power supply of the power source, e.g. battery 315 to the electrical components, such as the transceiver portion, of the device. During normal operation of the device, the switching arrangement 445 is controlled to supply power from the battery to all parts which need electricity. If a power failure, e.g. due to a glitch, is detected, the power backup controlling arrangement 444 redirects the function of the o power transforming circuit 490 so that the power stored in the capacitor 460 is transformed down to a suitable level for the electrical circuits in other portions of the device. The switch arrangement is controlled to redirect the down-transformed power from the flash capacitor 460 to the electronics of the device.

By doing so, the effect of the power failure is eliminated and the circuits needing power for 5 their operation are maintained operating.

The invention may detect the power glitches using a low voltage and/or current detector. A detector may be used to detect a power reduction down to a predetermined value.

It should be appreciated that the up/down transformation of the power to and from the capacitor is needed in cases that the capacitor is charged and discharged with higher0 voltage/current for operating the flash than the rest of the electronics. Thus, in cases the electronics of the devices operate with same voltage current level of the capacitor, the power may be supplied to the electronics without addition down transformation.

Clearly, other capacitive elements can be used in same way as the flash capacitor.

It should be noted that the word "comprising" does not exclude the presence of other5 elements or steps than those listed and the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, that the invention may be implemented at least in part by means of both hardware and software, and that several "means", "units" or "devices" may be represented by the same item of hardware. 0

The above mentioned and described embodiments are only given as examples and should not be limiting to the present invention. Other solutions, uses, objectives, and functions within the scope of the invention as claimed in the below described patent claims should be apparent for the person skilled in the art.